The present disclosure relates to an apparatus and method for diagnosing degradation of a lubricant in an internal combustion engine.
Japanese Examined Utility Model Publication No. H01-38250 describes estimation of the amount of soot formed based on the speed of an engine and the amount of fuel injected (i.e., an engine load), and diagnosis of degradation of oil based on the cumulative value of the amount of soot estimated. In this manner, the degradation of oil may be diagnosed with high accuracy based on the operational state of the engine.